Mathias was shipped from Cleveland to Milwaukee in exchange for minor-league catcher Andres Melendez on Wednesday.
Mathias was subsequently added to the Brewers' 40-man roster to protect him from selection in the upcoming Rule 5 draft. The 25-year-old hit a respectable .269/.335/.442 with 12 homers and 13 steals for Triple-A Columbus last season. He'd have a better chance to make a big-league bench if he could play shortstop, though he appeared there just three times last season, splitting most of his time between second and third.